hardware - TheTinyQRQkeyer

https://www.ebay.com/itm/155238850427 HAVE TO BE THE STM32F411CEU6 Black Pill which are prepared for flash. ( shall not be used but then you know it is the right board )

https://www.ebay.com/itm/402674756042  HAVE TO BE THE I2C version

https://www.ebay.com/itm/203080834192

https://www.ebay.com/itm/400985344220